But before we meet all those new faces properly next autumn, we still have a Christmas adventure left with the series’ current companion – Pearl Mackie’s Bill Potts – and in a new RadioTimes.com exclusive video, you can see exactly how she made the Tardis team back in 2016, as told by the stars and crew who were there at the time.

In the footage, taken from a 15-minute “Becoming The Companion” feature available on the Doctor Who series 10 DVD boxset from next week, Mackie looks back on how she was plucked from relative obscurity to read for a mysterious new role, forced to keep her potential sci-fi stardom a secret even while she auditioned with Peter Capaldi himself.

“She just felt very fresh, very modern, and she’d shown in her theatre work that she had quite a range, and that she had a sense of fun which is essential for this kind of role. “

“I had an availability check,” Mackie recalls, “and I was like, ‘Oh no, I’m not staying on for another year doing Curious Incident [of the Dog in the Night time]’

“And they were like, ‘Great – oh, well, that thing you just got availability checked for is actually to be the new companion in Doctor Who.’

“And I just burst out laughing. Like, ‘That’s amazing, amazing and hilarious, and I’m never gonna get that, am I?’”

Peter Capaldi and Pearl Mackie in their first Doctor Who appearance (BBC)

Soon though, on 8th March 2016 Mackie found herself auditioning for the role of Bill Potts in front of head writer Steven Moffat, accompanied by star Peter Capaldi – and a brand-new script.

“There’d be not a bit of point in asking her to audition as Clara,” Moffat says. “So I wrote maybe a slightly caricatured version of what I was looking for with Bill, so we could find the right person to do that sort of humour, that kind of irreverence.”

“The audition was very good,” Capaldi adds in the documentary. “I personally find the process of being around auditions very uncomfortable – because I’m an actor, so I tend to empathise with everybody, with all the actors. So I want to give everybody the job!”

“I was like, ‘What is happening here?’” Mackie concludes in the footage. “This is absolutely the most insane thing that’s ever happened to me.”

We’re sure Bradley, Tosin and Mandip are feeling exactly the same way today.

You can watch the full segment (including previously unseen behind-the-scenes footage) about Mackie’s Doctor Who casting in the video above, while the full Becoming the Companion documentary will be available on the special features of the Doctor Who series 10 boxset from next week along with many other unseen features.